Further Notes on Australian Hydroids. 113 



dense medium.* In. front view the hydrotheca appears very- 

 different to that of the other species, on account of the aperture 

 being of an oblong or elliptic form, due to the lateral margins 

 being erect instead of widely expanded, so that the aperture, 

 though long, is no wider than the body of the hydrotheca, while 

 in K. 7nirabilis the sides are strongly everted, contributing to 

 form the wide circular rim characteristic of that species. The 

 intrathecal ridge as seen in front view is not toothed or pointed 

 at the centre, but has the margin convex or sometimes nearly 

 straight. The mesial sarcothecae are variable in the extent to 

 which the upper loculus is developed, generally approximating in 

 form to those of the last species, but sometimes being much 

 narrowed at the sides ; those on the rachis are not constant in 

 number. The internodes of the stem may bear either one or two 

 hydrocladia. 



The gonangia being attached by the whole of the lower side, 

 the aperture is on the upper surface, close to the end, and is 

 formed by the rupture of the perisarc in a circular form ; at 

 least, such was the case in all the specimens I have examined 

 except one, which had the orifice partly terminal and partly 

 lateral, with the margin more distinctly outlined than usual. 

 The undulations on the upper surface are so faint as to be 

 scarcely perceptible except in dry specimens. 



Plumularia campanula. Busk. 



Marktanner-Turneretscherf states that the P. rubra of von 

 Lendenfeld is an unbranched but pinnate form of this species, a 

 conclusion which was to be expected, seeing that their minute 

 structure is identical, though they had not previously been found 

 in conjunction. Busk, however, in his original description of 

 P. campanula, mentioned that simple and branched shoots grew 

 together in the same colony, and there can be little doubt tliat 

 the hydrosoma always commences its growth as a simple shoot, 

 bearing hydrothecse, that it afterwards gives off pinnate hydro- 



» It is worthy of note tbat iu this and other species the terminal or newest hydrotliecse 

 occasionally retain their shape perfectly, while all tbe older parts of the perisarc are more or 

 less shrunken and distorted. 



t Die Hydroideu des k.k. uaturhistorischen Hofnuiseums, Wien, 1890. 



